Ultra-high temperature pasteurization, often called UHT where milk is ultra-pasteurized, and packaged in sterilized containers. It’s pure milk as you purchase it from the supermarket. But, the unique packaging and method make it last for a long time.

Although the majority of milk is processed by the traditional method of pasteurization, UHT milk undergoes ultra-high-temperature pasteurization which safely raises the temperature of milk up to a higher temperature, and kills harmful bacteria in the milk. The milk is stored in sterilized containers that are commonly referred to as aseptic packaging. This ensures that the milk remains fresher for a longer period.

UHT milk can be kept at room temperature for 3 months. But, it depends on the kind of brand. If the container has been open, the milk must be refrigerated and will have the same shelf-life as other types of dairy (7 or 10 days).

UHT Method

The most important elements of the UHT procedure are :

  • Heating, regardless of waiting for the right moment
  • Homogenization using the ultra high temperature pasteurization heating to temperatures appropriate for sterilization
  • The temperature for sterility is kept at a constant temperature.
  • Initial cooling
  • Homogenization (alternative method for direct or indirect methods)
  • Final cooling
  • Aseptic packaging

The preheating stage using HTST’s pasteurization equipment can increase temperatures by 5 and 90 degrees C by the sterilization process of hot milk. In some facilities, the milk is kept for a specific period of duration in a holding tube following the preheating process e.g. for 60 minutes at 95 degrees Celsius. The main reason is to reduce the risk of deposit formation and fouling in the subsequent heat exchangers. However, it may also affect the overall quality as a result due to the deactivation process of the milk’s naturally occurring enzyme.

The final heating step necessary to reach the sterilization temperature can be achieved by using one of two main types of heating methods: directly or indirectly. Direct methods heat the milk through direct contact with superheated steam to cook. Additionally, indirect systems use heat exchangers. In these systems, steam superheated by steam can be used to heat milk through a stainless steel layer that is insulated, that is made up of an elongated tube, or plates.

Once the sterilization temperature has been attained, the milk is stored in a sealed tube. The temperature of the milk and the amount of length of time it takes for it to pass through the tube it is in is the norm usually mentioned in the UHT procedure, e.g., 140 degrees C for 5 minutes.

The initial cooling of milk takes place immediately after it is transferred through a chamber vacuum which is later reduced to its original temperature of 75 ° C. At the end of each cooling stage direct-based systems, and the two cooling stages of indirect methods the heat generated by the heated milk can be transferred into cold milk through the regeneration or preheating process.

The homogenization process can also be part of the process of ultra high temperature pasteurization by Micro Thermics when fat is present in the product. The process takes with temperatures between 60-70 degrees C before and/or following the sterilization stage. This puts tremendous stress on the workers of the plant to ensure that homogenizers are sterilized.

That’s why it is suggested that, when possible, homogenization is essential before sterilization. It is generally accepted that the milk that is produced during natural healing processes needs to be homogenized in the future to break down the protein aggregates that form during healing that cause a sour flavor to the milk.

The process of packaging with aseptic seals is a necessity. The product needs to be transferred after cooling to the packaging and then sealed inside the container. There are various types of packaging available, but the most popular options include multilayered plastic and paperboard. It is then sterilized prior to filling.